


Tainted

by Amaraly



Category: Fire Emblem Series, Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Dark Magic, Established Relationship, Eventual Smut, Explicit Language, F/M, Fluff and Angst, Hurt/Comfort, Married Couple, My Unit | Byleth Has Emotions, Near Death Experiences, Not Beta Read, Porn With Plot, Post-Blue Lions Route (Fire Emblem: Three Houses), Post-Time Skip, Post-War, Pregnancy
Language: English
Status: In-Progress
Published: 2020-08-04
Updated: 2020-08-04
Packaged: 2021-03-05 21:21:57
Rating: Mature
Warnings: Graphic Depictions Of Violence
Chapters: 1
Words: 3,985
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/25722031
Author URL: https://archiveofourown.org/users/Amaraly/pseuds/Amaraly
Summary: After successfully surviving the war together, Felix and Byleth can finally focus on their married life and respective political obligations. But, with the expected birth of the new Fraldarius heir, and a cursed battle wound that never heals, can they uncover the true identity of their enemy before it's too late?Also know as: Byleth takes a blow for Felix, but ends up with an unknown curse.
Relationships: Felix Hugo Fraldarius & My Unit | Byleth, Felix Hugo Fraldarius/My Unit | Byleth
Comments: 2
Kudos: 28





	Tainted

**Author's Note:**

> I'm starved for more felileth content - let's enjoy this ride together everyone!
> 
> My Twitter for update news and randomness - @MaralXie

"Next time bring your friends" Felix spat the words as the enemy's body hit the ground with a loud wet thud.

The sniper, who has been focusing on him and Byleth for a while now, was hidden in the shadows of a nearby grove. Making him especially difficult, or as Felix preferred, annoying to locate and take down amidst the raging battlefield. 

This time, his lone wolf nature has cost him deeply. 

Too immersed in his duel with a Grappler, he failed to notice the quick arrow aiming for his blind spot. If it wasn't for Byleth he could hav-

"Tch" interrupting his thoughts from bringing up an unpleasant memory, Felix broke eye contact with the body. Finally allowing his sword hand to rest at his side. 

It's not that he was ungrateful for her protection, but surely Felix wasn't happy that his wife had to take the blow of an arrow because of his thick skull and, as Sylvain often remarked, "duel fetish". 

Guess he wouldn't have much credibility against his annoying best friend once this piece of news reached him. Comparing his training method to a fetish? The idiot sure has an insatiable appetite for depravity. 

The nerve of that one. 

Even so, what angered Felix the most was the fact that Sylvain had a point. At least this time for a change. 

In normal circumstances, he wouldn't be distracted to the point of missing an arrow with that amount of killing intent. He got lucky. 

Of course, Byleth didn't lack skill in any front, and so she managed to be merely scratched by the arrow while protecting him. A remarkable feat that didn't make him any less worried. Or pissed at himself.

Granted, these last enemies were part of what seemed to be today's last wave, but it didn't make Byleth's wound be any less of his fault. Specially because, something about it didn't sit right with him.

In their battle against the mysterious newfound group known as "those who slither in the dark", he felt like everything was staged, even the kingdom's army victory.

Their victory.

The moment his blade pierced that damned sniper. He couldn't just shake off, how the bastard kept on smiling. Grinning as Felix's silver sword twisted in his guts, spilling scarlet into the muddy floor. Even now, his blank dead stare held the peace of an accomplished pawn. 

"Disgusting" Felix whispered, half to himself and half to the enemy's deprived body. "To think I'd let a filthy psycho like yourself touch my wife". He admitted, back turned to the corpse as he approached the discarded bow nearby. 

Squatting for a quick examination, he took the weapon into his hands, fingertips exploring and massaging the mysterious material.

Aside from the unknown base material, adorning the weapon with a wicked black metallic shine, this seemed to be a regular longbow. Same with the arrows. Even so, if it wasn't for Byleth's expertise and skill, that blow could have easily killed any target within range. 

And, as much as he hated to admit it, even himself. Had she not intervened.

"This just doesn’t make any sense" Annoyance and frustration getting the best of him. 

Hundreds of enemy soldiers and this quality of weapon only shows itself now? To fight a losing battle in the hands of an unknown lone sacrifice pawn.

"Tch, I've got no time for this bullshit" snapping one arrow between his gloved hand, Felix strode back to reunite with his comrades. A new rush of adrenaline finally feeding his worries for Byleth's wellbeing.

Immediately after finishing the Grappler, he gave byleth a quick scan before proceeding to finish to job with the annoying sniper. But that wasn't nearly enough time to address the seriousness of her injury. 

And so, ignoring his dread as he took the pointy half of an arrow for further examination. Steady steps over dirt, Felix rushed to the after-battle barracks, as the evening sun gave place to the approaching summer night. 

***

"It seems the Boar King’s early speech had its effect" Felix noted, unconsciously remembering the last bit of Dimitri's discourse amidst the chaos of drunken soldiers.

"Should we win today's offence, those who slither in the dark no longer will have the capacity, nor the guts, to challenge our glorified and rightful kingdom. Fighting today, at my side, are the privileged men and women that will bring peace to Foldlan and its people once and for all. For the honor and peace of our families and loved ones, i ask you to lend me your strength once more, let's end this together!" Lifting Areadbhar, the royal family signature weapon, Dimitri finished his pre battle speech and successfully managed to raise the morale of a continent's army. 

The battle cry that soared after was something out of a history book. From the front lines to the logistic soldiers, everyone from different backgrounds cheered together, hugging and crying in their euphoria. Something Felix would never forget. As much as he hated to admit it, the rehabilitated boar king sure had a way with words.

Dimitri deserved the praise. For now, at least. The swordmaster settled as he passed through a sea of tents. All of them bursting with festivities, beverages and improvised music to celebrate today's final victory. 

Around a huge campfire, a particularly loud group of Pegasus Knights singed and danced to the music in a more than embarrassing manner. Without a care in the world. Eying the poor display of talent, Felix allowed himself to smile a little, as he continued on his way to the healing tents. 

With each step, reality seemed to slowly sit with him  
It was finally over now. The suffering. The bloodshed. And the meaningless deaths of allies, family and friends. They were set for a new beginning. At long last. 

Glenn… Father.

Approaching his initial destination, he stood checking the numbers of the healing tents one by one. As if in a trance, too scared to believe that everything was really over.  
Anxiety speaking louder than reason. A million worst case scenarios passed behind his stoic facade and, suddenly, it became too hard to breathe.  
I need to see her.  
He kept a firm pace. Breathing in and out. Step after step. 

The humid grass muffled the sound of boots outside healing tent 64. The number Annette and Flayn directed him to at the barracks entrance. Stiff outside the makeshift door, a relieved smile assaulted his expression at the sound of her voice.

"Thank you Mercedes! it was barely a scratch already, but now I can move my arm around without any semblance of pain. Your healing skills and whim never cease to amaze me" 

"Oh professor, there no need for such praise! You deserve all the care. Just make sure not to touch or move that bandage around too much ok?" 

Felix let out a sigh he didn't know he was holding. She was okay. Alive, laughing and healthy. Just seconds away from him.  
And suddenly, that seemed like too much distance. 

"oh professor! It's seems like we've got company!" 

And so, he barged into tent 64. 

***

Once again, inspired by Mercedes's nurturing nature, Byleth caught herself imagining what having a mother felt like. 

As they both laughed her pain away, Mercedes's gentle hands and warm healing magic made her feel like a precious little doll. Too cherished to bear even the tiniest of scars. The favorite among hundreds of candidates.

Never too particular about her appearance. These moments, when someone cared for her, made Byleth's cheeks burn a bit too much for her own good. 

But she didn't care. Not right now.

Since Edegalrd's defeat, and the subsequent discoveries of those who slither in the dark, it would be their first time living free of war. In peace.

At long last. 

"..." 

Unconsciously she closed her eyes, focusing on the comfortable ticklish sensation of the healing magic. 

It felt familiar yet foreign. The sensation of being taken care of.

It's not that she lacked love growing up. Sure, having her emotions sealed up by a sleepy goddess inside her head had its implications on her experience of emotions. But she never felt incomplete.

First, it was Jerald. The ever present yet distant father figure was, for the majority of her life, her only real bond. He was her solid ground. Stern, yet always supportive. 

And then, thanks to him, Byleth met her precious students-

"Hmm hmmm, hm hmmm" 

A small giggle escaped Byleth at the sound of Mercedes humming innocently. Too focused on fixing her arm bandage to notice anything else. 

Yes, thanks to Jerald she met her students. The infamous Blue Lions house that devoured other houses students. That Blue Lions house, whose passion conquered more members than a classroom could possibly fit. 

House of promising youths. That looked up to her with sparkling eyes. Each one of them with a whole universe of emotions, expectations, dreams and ambitions. She swore most of the time she was the one doing the learning part of the bargain. Naturally. 

And then, just like that, she met him. 

At first, sharp words and blades seemed to be the only languages he knew. The boy who spoke thought duels rather than words. Felix. 

Not that her stoic self from the time had any complaints. 

In that regard, they were the same. 

Swords meeting before words. Actions above promises. And the hunger for victory above all else. 

Yes, that's how they began. How they found each other's answers, dreams, hopes and ambitions together. Fighting.

And so they fought to the point of desire. Bodies and souls asking, imploring and demanding more. More of each other. Not only as training partners, colleagues or friends. They needed everything of each other. Every weakness and strength. Every flaw and quality. All fears and anxieties as well as the will to move on. 

Every drop of blood, sweat and tears. 

Everything.

Yes, he was her everything. His warm red eyes being her favorite mirror. Where she smiled the most and cried the most when life was too much to handle. Where she finally found and accepted everything that she was. Not a lifeless god vessel, but Byleth and all the implications that brought. The sins. 

"Just Byleth". She recalled his calm yet sure voice, whispering next to her ear.

"We're almost done professor! I'm just making sure this last scratch won't leave a scar" voice suddenly pulling Byleth out of her daydreams. 

it was already dark outside. Surely, he would arrive soon to check up her. This, or he was already by the door catching his breath. The thought brought a smile to her face. 

Voice full of enthusiasm she replied. 

"Thank you Mercedes! it was barely a scratch already, but now I can move my arm around without any semblance of pain. Your healing skills and whim never cease to amaze me" 

From the looks of it, she really seemed to be almost done. 

Looking up from her work surprised, Mercedes's eyes suddenly sparked with joy as she fixed her gaze in the makeshift door.

"Professor! It's seems like we've got company!" Still smiling she clasped her gloved hands together. 

“Oh really?” Faking ignorance, Byleth suppressed a chuckle. Sitting frame slowly turning to the door ”I wonder who-” She didn’t manage to fish her sentence. Couldn't, as strong arms embraced her half turned frame gently, but firmly. Face hidden on his shoulder, her body relaxed as she inhaled the familiar scent, cedar with hints of lavender, fresh yet calming. His scent.

“I’m back” Felix said, matter of factly. Pressing her even closer, he planted a kiss to her temple. 

Face still hidden inside his hug, Byleth let out a toothy grin and a whisper, as a confession to his fast beating heart. 

“Welcome Home” 

“...”

“My, my…” A low male voice interrupted, with not so hidden amusement at the situation “Well Ingrid, I guess we really did came at a bad time.” He chuckled. “ Or maybe... we got lucky. It's not everyday we see Felix and Professor all... buddy buddy~ like this”

“Sylvain... “ A much less pleased tone came in reply right after. “First, they´re married. And second..” Ingrid pointed to a very red eared Felix, who still had his back turned to them, in a failed attempt to pretend that any of this wasn’t happening, “Stop teasing Felix, or next time he might actually cut you down” She sighed. “And I won’t stop him this time.”

“Worth it” 

“Well…” Previously absent from the room in respect for the reunited couple’s intimacy, Mercedes popped out of a curtain hugging herself with a huge blush on her cheeks. “He’s got a point Ingrid, it was absolutely sweet and cute!” 

“ What! OUR little Felix!? being sweet AND cute...“ 

Surprised at how well behaved Felix seemed to be at the whole ordeal, Byleth looked up to get a glimpse of his face. And boy, it was worth it. Mouth pressed into a thin line and face as red as fresh tomato, Felix’s brows were mindblowingly furrowed. The fact that even Mercedes, of all people, decided to tease him was just too much to handle apparently. 

Slowly letting go of Byleth, Felix turned around to face his friends with the best annoyed expression could he master at the time. Red face and all.

“Don’t you have anything better to do?” With his trademark sharp tong, he continued. “Of all places… why the fuck are you even here!? Is it your goddam nurse kink again? if so…” He said, unsheathing his sword confidently. “I’ll gladly help you prolong your stay here” 

“Wait! Felix there’s no need to-’

Suddenly, an unexpected laugh caught their attention. 

“Pfft-” Timid at first, in an instant it grew in volume. “haha HAHAHAHA” 

All at once, Felix, Sylvain, Ingrid and Mercedes stared at Byleth at a complete loss of words. Previous discussion long forgotten.

Of course, Felix was pissed beyond comprehension thanks to his friends antics, but still.. Seeing Byleth laughing like this, he honestly felt like all that embarrassment was worth it. Not that he would ever admit it out loud.

Putting his sword back, Felix looked the other way in defeat. At the sound of Byleth, Mercedes and Ingrid laugh, Sylvain’s only response was a quick wink at his friend. Apologetic or not, Felix decided it sufficed for now. 

“What are you guys still doing here?” Standing by the tent’s entrance, with what seemed to be a strawberry alcoholic drink, was Annette. Cheeks almost the same color as the drink, she continued. “C’moooon let’s celebrate properly!” Voice and body language indicating that the pink thingy was, indeed, alcoholic.

Without any remaining patients at her post, Mercedes was the first one to stand up. Discarding her medical gloves and equipment, she followed Annette out of the tent. Giving the others an apologetic, yet smug glare. 

“Well, that was actually what we came here for.” Ingrid said, standing up while massaging her calloused palms. “We’ve got a pretty good spot near the beer stock, we can even sit down and- Hey!?” Interrupted by Sylvain, carrying her out of the tent all of a sudden, she struggled to keep her balance over his shoulder. 

“Yeah, yeah. Time out, I think I saw someone trying to steal our spot” 

“What!? But I told Ashe to keep watch! How can you even tell from here?”

“Call it intuition. We gotta run to save it, and fast. Geez” Already at the entrance, Sylvain stopped in his tracks sending Felix a cocky look “I’m such a good friend, the best even.” Smirking, he held the last piece of the fabric door still keeping him inside. “That’s why Ingrid and I will go first to grant that sweet spot next to the bar, ok? You take care of Byleth and meet us there when everything is already taken care of.”

Without another world, he left into the night with Ingrid on his back. Leaving Felix and Byleth completely alone inside.

Despite the comfortable silence, she was the one to break the atmosphere. 

“So, what’s this in you pocket” Referring to the snapped black arrow he brought from the sniper, she pointed at it with a playful curious expression. “ A souvenir perhaps?”

“This? Nah, got it from that bastard shooting at us from the woods ”holding it between his thumb and middle finger, he skilfully rolled it around in his hands to show her it's odd materials. "Despite it's fancy looks, it didn't do much against my sword" he guaranteed, sensing Byleth's worry. Arrow now settled into the dark wood table adorning the center of the tent.

"I see" putting a hand above her bandaged upper arm, she caressed the wound lightly, wearing a distant smile. "I'm just glad you're safe"

Felix knew that expression, that melancholy that casted shadows upon her eyes. The one she always had when dealing with a troublesome inner struggle, or a particular disturbing memory she wished to forget. Of course, most times she wasn't able to. And so, she would go to him in a desperate need to be heard, to be validated.

To be forgiven. 

He, of course, always stood by her side. To lend an ear, a shoulder or anything she needed at the time really. It could happen randomly, but usually nightmares would cause such a state. It wasn't a frequent occurrence, but still, he was only thankful for being there, to hold and love her until she managed to sleep again. 

Felix knew her better than anyone, in and out. Even with the outbreak of a war right after their wedding, nothing really kept then apart for too long. And so, naturally, she told him her secrets. Things she didn't bear to hide anymore. 

Starting with one of her biggest battle assets, the Divine Pulse.

Mesmerized at first at Byleth's skill to bend the future to her will, he soon understood how that was also a double edged sword. 

First, it required a large amount of her energy, tiring her out easily during battles. But the worst of all, was the psychological strain it represented. 

It's limited uses per battle represented a choice everytime Byleth confronted death on the battlefield. Essentially, a choice of who lives or dies. Whose death would be beneficial, whose death would be "acceptable" this time.

Indeed this was a power, and a choice, worthy of a goddess. Or a cold blooded goddess vessel. Not a human. Not the woman Byleth was now. The woman she unleashed after years of nurturing bonds with her friends and loved ones.

Beating or not, one’s heart is also a double edged blade. And this is what hurt the most. It was because of them that she suffered that much every time.

And Felix could tell this time it was because of him.

"Did I die?" Blunt, he knew, but he didn't want her being the only on one to know any second longer. "Would I die to that arrow?" 

Hesitant, but fast, came a reply

"Yes.." voice shaky, she averted her gaze. 

It's never easy to know your death. To know for certain the full extent of the consequences of your actions. The so called "what if" scenarios. But, in that moment Felix had to be strong for her.

“Thank you” he said with a gentle squeeze to her shoulder. “I won’t apologise.. and I won't ask any more. What matters is that I’m here now, with you.” With a bittersweet expression he continued, “I guess that's why I didn’t feel any killing intent huh?” 

“What do you mean?”

“Well, with your hawk-like watch on my back ” With a playful smirk, he ruffled her already unruly hair. “There’s no way anything would actually get close enough to seriously injure me” intertwining their fingers he kissed the back of her hand, never breaking eye contact. “You won this round.”

“Hehe” Mood lighting instantly at the mention of their endless competitiveness, hooking an arm around his neck she teased “Is that so…” Lips mere centimeters away she pressed further. “In this case, I might just collect my reward"

Slowly pressing her down on the table, he locked his fingers around the wrist of her bandaged arm. “Are you sure you can handle it any time soon?” purposefully eying her injury, he gently let go of her wrist, to send a signal that he wouldn't risk opening the recent wound. As much as he wanted to indulge in his lust for her. 

"Oh please, this?" Moving her arm around with ease, she standed up reaching for the broken arrow "I'm good as new Felix, this ugly little thing couldn't eve- AGH!" 

Byleth's hand instinctively cluched her injury.

Suddenly, she felt a snapping pain burning through her whole body. Arching forward in response, the immense pain disappeared as soon as it made itself known. 

Broken arrow falling to the grond. 

"Byleth? Hey, Byleth! Are you okay!?" Warm hands and a worried tone brought her back to reality. 

And all that immense pain suddenly seemed like a nightmare, a mere product of her exausted imagination. 

"Yeah, I'm just… light headed all of sudden" 

"You've been through a lot today. Just don't.. strain yourself anymore. I'm here now." Helping her sit down on a nerby chair, Felix picked up the arrow again as she looked to the opposite side. Now hid inside his battle robes, he would make sure to ask Seteth to investigate it as soon as possible. "We should go to our quarters for the night." 

It was too much of a coincidence. Far too much to be pure chance. 

The strange weapon. The lack of killing intent directed at him. The crooked smile of his opponent. As now this. Such immense pain immediately after touching the material. 

"No, it's okay." Standing up with confidence, she made to the door. Hands on his, she pulled him towards the heating party just outside. "Everyone made the efford to look for us here, they even got a table in a mess like this. They deserve this celebration" Noticing he was still not budging she pressed. "We deserved it too, after all we've been through.." 

"Right.." finally moving to join her at the exit, he reprocicated her warm grip "But only for a little while, more of this maddeness and I might loose it for real with a drunk Sylvain"

"Good enough, I'm not really a party person myself" 

"Then, why are we going again..?" 

Byleth said on different occasions how overprotective he was sometimes. Of course his wife wasn't a weak woman, but this was on a completely different scale. Everyone was relaxed, but at the same time they knew too little about the soposedly defeated group. 

Would a synister underground mage group really challenge a whole continent, after centurys of better opportunities. Would they rise to the challenge without a clear way to victory, even after all this time? 

She interrupted this train of thought

"Because I won today right?" With a playful smile she continued. "Give me some slack today, no questions" 

"Are you sure you want to spend your reward in a place like this" 

"The day only ends when we sleep"

"..."

Ever since they got together, one of the things he appreciated the most was how wicked she managed to be while still wearing a neutral detached expression. Byleth always played all her cards like a true warrior. Boring knights and their fake honor could just go fuck themselves.

Somehow, he felt like she had just won a secret duel right there right now. 

Seriously this woman would be the death of him. 

Hand in hand, they walked into the night. Under the gentle light of the summer moon, they laughed together with friends and colleagues.

Despite the black skies outside, soon wound come the taint of true darkness, as they delved deeper into the unknown. 

Deeper into the abyss.

**Author's Note:**

> Thank you for taking to time to read! 
> 
> I just can't get enough of Felix being a total worrywart when it comes to Byleth, not to mention competitive. 
> 
> Felix: smugly wearing "no fear" shirt  
> Sylvain: "Byleth dying™" shirt  
> Felix: upgrades to - "one fear" 
> 
> I'm not very experienced with creative writing, so any feedback would be appreciated. 
> 
> Be gentle (๑´•.̫ • `๑)


End file.
